6 channel output dolby surround (RCA) to Digital or HDMI

[Rj Bob]

I have a 6 channel surround sound processor that has only 6 RCA jacks out, I want to hook this up to my bose lifestyle 38 series 4 with HDMI... or coaxial

 

[kanewolf]

I do not see a 5.1 encoder anywhere that I searched. Lots of devices that go the other way, but not analog to digital.